From 1e688dd2a3d6759d416616ff07afc4bb836c4213 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Tue, 13 Apr 2021 16:38:10 +0000 Subject: [PATCH] powerpc/bug: Provide better flexibility to WARN_ON/__WARN_FLAGS() with asm goto Using asm goto in __WARN_FLAGS() and WARN_ON() allows more flexibility to GCC. For that add an entry to the exception table so that program_check_exception() knowns where to resume execution after a WARNING. Here are two exemples. The first one is done on PPC32 (which benefits from the previous patch), the second is on PPC64. unsigned long test(struct pt_regs *regs) { int ret; WARN_ON(regs->msr & MSR_PR); return regs->gpr[3]; } unsigned long test9w(unsigned long a, unsigned long b) { if (WARN_ON(!b)) return 0; return a / b; } Before the patch: 000003a8 : 3a8: 81 23 00 84 lwz r9,132(r3) 3ac: 71 29 40 00 andi. r9,r9,16384 3b0: 40 82 00 0c bne 3bc 3b4: 80 63 00 0c lwz r3,12(r3) 3b8: 4e 80 00 20 blr 3bc: 0f e0 00 00 twui r0,0 3c0: 80 63 00 0c lwz r3,12(r3) 3c4: 4e 80 00 20 blr 0000000000000bf0 <.test9w>: bf0: 7c 89 00 74 cntlzd r9,r4 bf4: 79 29 d1 82 rldicl r9,r9,58,6 bf8: 0b 09 00 00 tdnei r9,0 bfc: 2c 24 00 00 cmpdi r4,0 c00: 41 82 00 0c beq c0c <.test9w+0x1c> c04: 7c 63 23 92 divdu r3,r3,r4 c08: 4e 80 00 20 blr c0c: 38 60 00 00 li r3,0 c10: 4e 80 00 20 blr After the patch: 000003a8 : 3a8: 81 23 00 84 lwz r9,132(r3) 3ac: 71 29 40 00 andi. r9,r9,16384 3b0: 40 82 00 0c bne 3bc 3b4: 80 63 00 0c lwz r3,12(r3) 3b8: 4e 80 00 20 blr 3bc: 0f e0 00 00 twui r0,0 0000000000000c50 <.test9w>: c50: 7c 89 00 74 cntlzd r9,r4 c54: 79 29 d1 82 rldicl r9,r9,58,6 c58: 0b 09 00 00 tdnei r9,0 c5c: 7c 63 23 92 divdu r3,r3,r4 c60: 4e 80 00 20 blr c70: 38 60 00 00 li r3,0 c74: 4e 80 00 20 blr In the first exemple, we see GCC doesn't need to duplicate what happens after the trap. In the second exemple, we see that GCC doesn't need to emit a test and a branch in the likely path in addition to the trap. We've got some WARN_ON() in .softirqentry.text section so it needs to be added in the OTHER_TEXT_SECTIONS in modpost.c Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/389962b1b702e3c78d169e59bcfac56282889173.1618331882.git.christophe.leroy@csgroup.eu --- arch/powerpc/include/asm/book3s/64/kup.h | 2 +- arch/powerpc/include/asm/bug.h | 54 +++++++++++++++---- arch/powerpc/include/asm/extable.h | 14 +++++ arch/powerpc/include/asm/ppc_asm.h | 11 +--- arch/powerpc/kernel/entry_64.S | 2 +- arch/powerpc/kernel/misc_32.S | 2 +- arch/powerpc/kernel/traps.c | 9 +++- scripts/mod/modpost.c | 2 +- .../powerpc/primitives/asm/extable.h | 1 + 9 files changed, 72 insertions(+), 25 deletions(-) create mode 120000 tools/testing/selftests/powerpc/primitives/asm/extable.h diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h index a1cc73a88710..170339969b7c 100644 --- a/arch/powerpc/include/asm/book3s/64/kup.h +++ b/arch/powerpc/include/asm/book3s/64/kup.h @@ -90,7 +90,7 @@ /* Prevent access to userspace using any key values */ LOAD_REG_IMMEDIATE(\gpr2, AMR_KUAP_BLOCKED) 999: tdne \gpr1, \gpr2 - EMIT_BUG_ENTRY 999b, __FILE__, __LINE__, (BUGFLAG_WARNING | BUGFLAG_ONCE) + EMIT_WARN_ENTRY 999b, __FILE__, __LINE__, (BUGFLAG_WARNING | BUGFLAG_ONCE) END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_BOOK3S_KUAP, 67) #endif .endm diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h index d844de5adfcb..1ee0f22313ee 100644 --- a/arch/powerpc/include/asm/bug.h +++ b/arch/powerpc/include/asm/bug.h @@ -4,6 +4,7 @@ #ifdef __KERNEL__ #include +#include #ifdef CONFIG_BUG @@ -30,6 +31,11 @@ .endm #endif /* verbose */ +.macro EMIT_WARN_ENTRY addr,file,line,flags + EX_TABLE(\addr,\addr+4) + EMIT_BUG_ENTRY \addr,\file,\line,\flags +.endm + #else /* !__ASSEMBLY__ */ /* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3 to be FILE, LINE, flags and sizeof(struct bug_entry), respectively */ @@ -58,6 +64,16 @@ "i" (sizeof(struct bug_entry)), \ ##__VA_ARGS__) +#define WARN_ENTRY(insn, flags, label, ...) \ + asm_volatile_goto( \ + "1: " insn "\n" \ + EX_TABLE(1b, %l[label]) \ + _EMIT_BUG_ENTRY \ + : : "i" (__FILE__), "i" (__LINE__), \ + "i" (flags), \ + "i" (sizeof(struct bug_entry)), \ + ##__VA_ARGS__ : : label) + /* * BUG_ON() and WARN_ON() do their best to cooperate with compile-time * optimisations. However depending on the complexity of the condition @@ -70,7 +86,15 @@ } while (0) #define HAVE_ARCH_BUG -#define __WARN_FLAGS(flags) BUG_ENTRY("twi 31, 0, 0", BUGFLAG_WARNING | (flags)) +#define __WARN_FLAGS(flags) do { \ + __label__ __label_warn_on; \ + \ + WARN_ENTRY("twi 31, 0, 0", BUGFLAG_WARNING | (flags), __label_warn_on); \ + unreachable(); \ + \ +__label_warn_on: \ + break; \ +} while (0) #ifdef CONFIG_PPC64 #define BUG_ON(x) do { \ @@ -83,15 +107,24 @@ } while (0) #define WARN_ON(x) ({ \ - int __ret_warn_on = !!(x); \ - if (__builtin_constant_p(__ret_warn_on)) { \ - if (__ret_warn_on) \ + bool __ret_warn_on = false; \ + do { \ + if (__builtin_constant_p((x))) { \ + if (!(x)) \ + break; \ __WARN(); \ - } else { \ - BUG_ENTRY(PPC_TLNEI " %4, 0", \ - BUGFLAG_WARNING | BUGFLAG_TAINT(TAINT_WARN), \ - "r" (__ret_warn_on)); \ - } \ + __ret_warn_on = true; \ + } else { \ + __label__ __label_warn_on; \ + \ + WARN_ENTRY(PPC_TLNEI " %4, 0", \ + BUGFLAG_WARNING | BUGFLAG_TAINT(TAINT_WARN), \ + __label_warn_on, "r" (x)); \ + break; \ +__label_warn_on: \ + __ret_warn_on = true; \ + } \ + } while (0); \ unlikely(__ret_warn_on); \ }) @@ -104,8 +137,11 @@ #ifdef __ASSEMBLY__ .macro EMIT_BUG_ENTRY addr,file,line,flags .endm +.macro EMIT_WARN_ENTRY addr,file,line,flags +.endm #else /* !__ASSEMBLY__ */ #define _EMIT_BUG_ENTRY +#define _EMIT_WARN_ENTRY #endif #endif /* CONFIG_BUG */ diff --git a/arch/powerpc/include/asm/extable.h b/arch/powerpc/include/asm/extable.h index eb91b2d2935a..26ce2e5c0fa8 100644 --- a/arch/powerpc/include/asm/extable.h +++ b/arch/powerpc/include/asm/extable.h @@ -17,6 +17,8 @@ #define ARCH_HAS_RELATIVE_EXTABLE +#ifndef __ASSEMBLY__ + struct exception_table_entry { int insn; int fixup; @@ -28,3 +30,15 @@ static inline unsigned long extable_fixup(const struct exception_table_entry *x) } #endif + +/* + * Helper macro for exception table entries + */ +#define EX_TABLE(_fault, _target) \ + stringify_in_c(.section __ex_table,"a";)\ + stringify_in_c(.balign 4;) \ + stringify_in_c(.long (_fault) - . ;) \ + stringify_in_c(.long (_target) - . ;) \ + stringify_in_c(.previous) + +#endif diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h index 116c1519728a..ffe712307e11 100644 --- a/arch/powerpc/include/asm/ppc_asm.h +++ b/arch/powerpc/include/asm/ppc_asm.h @@ -10,6 +10,7 @@ #include #include #include +#include #ifdef __ASSEMBLY__ @@ -752,16 +753,6 @@ END_FTR_SECTION_NESTED(CPU_FTR_CELL_TB_BUG, CPU_FTR_CELL_TB_BUG, 96) #endif /* __ASSEMBLY__ */ -/* - * Helper macro for exception table entries - */ -#define EX_TABLE(_fault, _target) \ - stringify_in_c(.section __ex_table,"a";)\ - stringify_in_c(.balign 4;) \ - stringify_in_c(.long (_fault) - . ;) \ - stringify_in_c(.long (_target) - . ;) \ - stringify_in_c(.previous) - #define SOFT_MASK_TABLE(_start, _end) \ stringify_in_c(.section __soft_mask_table,"a";)\ stringify_in_c(.balign 8;) \ diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 15720f8661a1..70cff7b49e17 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -309,7 +309,7 @@ _GLOBAL(enter_rtas) */ lbz r0,PACAIRQSOFTMASK(r13) 1: tdeqi r0,IRQS_ENABLED - EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING + EMIT_WARN_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING #endif /* Hard-disable interrupts */ diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S index 39ab15419592..d8645efff902 100644 --- a/arch/powerpc/kernel/misc_32.S +++ b/arch/powerpc/kernel/misc_32.S @@ -237,7 +237,7 @@ _GLOBAL(copy_page) addi r3,r3,-4 0: twnei r5, 0 /* WARN if r3 is not cache aligned */ - EMIT_BUG_ENTRY 0b,__FILE__,__LINE__, BUGFLAG_WARNING + EMIT_WARN_ENTRY 0b,__FILE__,__LINE__, BUGFLAG_WARNING addi r4,r4,-4 diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index c8f648727d36..51d4f5faf425 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -1477,8 +1477,13 @@ static void do_program_check(struct pt_regs *regs) if (!(regs->msr & MSR_PR) && /* not user-mode */ report_bug(bugaddr, regs) == BUG_TRAP_TYPE_WARN) { - regs_add_return_ip(regs, 4); - return; + const struct exception_table_entry *entry; + + entry = search_exception_tables(bugaddr); + if (entry) { + regs_set_return_ip(regs, extable_fixup(entry) + regs->nip - bugaddr); + return; + } } _exception(SIGTRAP, regs, TRAP_BRKPT, regs->nip); return; diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 270a7df898e2..1209e1786af7 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -931,7 +931,7 @@ static void check_section(const char *modname, struct elf_info *elf, ".kprobes.text", ".cpuidle.text", ".noinstr.text" #define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \ ".fixup", ".entry.text", ".exception.text", ".text.*", \ - ".coldtext" + ".coldtext", ".softirqentry.text" #define INIT_SECTIONS ".init.*" #define MEM_INIT_SECTIONS ".meminit.*" diff --git a/tools/testing/selftests/powerpc/primitives/asm/extable.h b/tools/testing/selftests/powerpc/primitives/asm/extable.h new file mode 120000 index 000000000000..6385f059a951 --- /dev/null +++ b/tools/testing/selftests/powerpc/primitives/asm/extable.h @@ -0,0 +1 @@ +../../../../../../arch/powerpc/include/asm/extable.h \ No newline at end of file